Audio Systems: car system install question, rca cables, inch subs

Question
hey my name is karlos and im gonna be installing a system in my car i wanna get a pioneer premier headunit which has 3 pre amp outputs i wanna know what the rca's are used for in a system, im also plannin to get 2 10 inch subs n im deciding on a 2ch amp for now i would no be powering the speakers only the sub's but i want to know what the RCA cables are for in a system and what do they do?

Answer
Karlos,

 the RCA preouts on the back of a head unit provide the amp or amp's with the sound signal, some head units have certain preouts for certain applications such as a "subwoofer" preout that allows control from the head unit before the sound ever reaches the amplifier... YOU NEED RCA PREOUTS on your head unit .. all amplifiers use these , some lower quailty unit dont always have the RCA's as does stock factory units.. hope this helps you out if you need anything else let me know

thanks